1. Field of the Invention
This invention relates to a process for preparing polyolefins using a novel polymerization catalyst. More particularly, it is concerned with a process for preparing polyolefins which comprises polymerizing or copolymerizing olefins using a catalyst, said catalyst being prepared by mixing and heating an aluminum oxide and an ammonium sulfate, supporting a titanium compound and/or a vanadium compound, which are each a component of a Ziegler catalyst, on the resulting product as carrier and thereafter activating the resulting mixture with an organometallic compound.
2. Description of the Prior Art
In the technical field of this sort there have heretofore been known catalysts consisting of various inorganic solids as carrier and compounds of transition metals such as titanium and vanadium supported thereon. Typical of such inorganic carrier are mentioned alumina, titanium dioxide, zirconia, silica, thoria and magnesia (see, for example, Japanese Patent Publication No. 25353/69).
However, catalysts prepared by using the above-mentioned carriers, then supporting thereon a transition metal compound(s) such as titanium compound and/or a vanadium compound which are each a component of a Ziegler catalyst and thereafter activating with an organometallic compound, are disadvantageous in that the activity of those catalysts is generally low. Among the above-mentioned carriers, magnesia is known to give a relatively high activity, but alumina and silica have only afforded extremely low activity catalysts.
On the other hand, in the production of polyolefins, the polymerization activity is desired to be as high as possible. If the polymerization activity is high, it is not only possible to reduce the cost of catalyst, but also to prepare polyolefins in high yield at low partial pressure of monomer and in a short period of time; in addition, the procedure of catalyst removal which is usually required becomes simplified or, in some cases, may be omitted, with only a small amount of ash remained in the resulting polymer and the polymer being fully fit for practical use; and thus the process becomes extremely simplified as a whole. From this point of view, many of the catalyst systems using the above-mentioned inorganic carriers as they are have a low activity and thus improvements have been considered necessary.